Apparatus for automatically filling well casing



J. R. BAKER Nov. 22, 1955 APPARATUS FOR AUTOMATICALLY FILLING WELL CASING Filed April 2, 1954 2 Sheets-Sheet l (EH/v B. BAKEQ,

INVENTOR.

NX i4 M MM .47- TOQNEYS Nov. 22, 1955 J. R. BAKER 2,724,443

APPARATUS FOR AUTOMATICALLY FILLING WELL CASING Filed April 2, 1954 2 Sheets-Sheet 2 I 24- 1 -.25 26 I 15 J27 26 a l d 60 W 44 37 w 1! g -51 45 L H 52 I 55 3 2a 36 u (To/41v R. BAKE/8,

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2,724,443 Patented Nov. 22, 1955 United States Patent APPARATUS FOR AUTOMATICALLY FILLING WELL CASIN G Application April 2, 1954, Serial No. 420,5Qli 15 Claims. (or. 166-225) The present invention relates to subsurface well tools, and more particularly to well conduit apparatus for automatically controlling the filling of the well conduit with fluid while it is being lowered in the well bore.

.An object of the invention is to provide an improved apparatus for controllably filling a string of well casing, and the like, while it is being lowered in thewell bore, the fluid level internally of the casing being prevented from rising above a predetermined level, which is below the fluid level in the well .bore externally of the casing.

Another object or" theinvention is to provide an apparatus for controllably filling a string of well casing embodying an internal mechanism which is readily drillable to facilitate removal of the internal structure of the apparatus by adrill bit after the apparatus has served its purpose.

A further object of the invention is to provide an apparatus for controllably filling a string of. well casing while it is being lowered in the .well bore, which is also capable of being operated to prevent upward or backflow of fluid in the casing string, the apparatus possessing a comparatively short over-all length, enabling it to be manufactured more economically. Moreover, the shorter length entails a lesser amount of internal mechanism to be drilled out after the apparatus has served Yet another object of the invention is to provide an apparatus that formspart of a well casing string, embodying a valve mechanism which controls the filling of the casing string while the latter is beinglowered in the well bore, and which also functions asaback pres-:

sure valve to prevent upward flow of fluid in the well casing after the latter has been lowered to its desired depth in the well bore. d

Still further object of the invention isto provide an apparatus for controllably filling a string of well casing with the Well bore fluid to a level less than the external fluidlevel, in which the friction between relatively moving parts is reduced considerably, the apparatus bemg operable effectively and satisfactorily without the necessity for maintaining close manufacturing tolerances and for accurately fitting the parts.

This inventionpossesses many other advantages, and has other objectswhich may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification.. It will now be described in. detail, for the purpose of illustrating the generalprinciples of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a longitudinal section through an apparatus embodying the invention, with the valve mechanism dis posed in closed position toprevent upward fiow of fluid in the casing string;

Fig. 2 is a view similar to Fig. 1, disclosing the valve mechanism in open positionto permit upward flow of fluid in the casing string;

Fig. 3 is a cross-section taken along the line 3--3 on s- Fig. .4 is a view similar to Fig. l, disclosing the internal mechanism in a position permitting downward flow of fluid through the apparatus;

Fig. 5 is a view similar .to Fig. l, disclosing the valve mechanism acting asa back pressure valve to prevent upward or return flow of fluid in the casing string;

Fig. 6 is an enlarged fragmentary longitudinal section through a portion of the valve mechanism.

The apparatus A asspecifically disclosed in the drawings is a casing shoe adapted to form the lower end of a string of easing B to be lowered through the fluid in a well bore. It is to be understood, however, that the apparatus could be incorporated at any desired intermediate point in the casing, in which event it would be considered to be a casingcollarforming part of the casing string.

As disclosed, the casing shoe A includes an outer tubular member 10 which may have an upper threaded box 11 threadedly secured to the lower pin end 12 of an adjacent casing section, B. A valve mechanism is disposed within the tubular member. This mechanism is of the type which will allow the fluid in the well bore to flow upwardly into the casing string B while the latteris being loweredinthe well bore, but when the casing string has been lowered to the desired extent in the well bore, the valve mechanism can be placed in a condition in which it can preclude upward flow of fluid in the well casing, while permitting fluid to be pumped down through the well casing B and out through the casing shoe A.

The valve mechanism is constituted by an outer housing or valve body 13 which is secured to the tubular member it through the agency of an intermediate cementitious plug 14. This plug is inseparably united to the tubular member by providing internal longitudinally spaced circumferential grooves 15 therein, in which the ceinentitious material is cast. The lower end 16 of the cement plug is rounded or tapered to provide a guiding nose for the shoe in order to appropriately steer the casing past obstructions that might be encountered in the well bore during its lowering therewithin. The outer housing 13 is also provided with longitudinally spaced, circumferential external grooves 17 in which the cementitious material is cast. The upper end of the cement plug 114, as well as its lower end, has a passage 18 therethrough through which fluid can flow.

For convenience of assembling the apparatus, the valve housing or body 13 is made in several sections. Thus, an upper section 19 is disposed in the cementitious plug and has an upper valve seat 2t thereon adapted to be engaged by an upwardly facing tapered surface 2l on a valve head 22, when the latter is permitted to move in an upward direction to a sufficient extent, as described hereinbelow. This upper section 19 abuts an intermediate enerally cylindrical housing member 23, which, in turn, abuts a lower housing section 24, in the form of a spider having a central hub 25 connected to the outer portion of the lower section 24 by a plurality of circumferentially spaced ribs 26, these ribs defining openings 27 through which fluid can pass.

A valve stem or guide 23 has its lower portion 29 slidable through the spider hub 25, this stem having an intermediate enlarged portion 3% providing a downwardly facing shoulder 31 that initially rests on the upper end of the hub 25, to prevent downward movement of the valve stem or guide 28. Upward movement of the valve stem or guide is initially prevented by piloting the upper portion of the enlarged stem section within the hub 32 of a holding or stop spider 33 slidably engageable with the cylindrical wall 34 of the intermediate housing section 23. An annular valve seat 35- rests uponthe outer portion 36 of the holding spider, this seat being prevented from moving in an upward direction by engaging the lower end 37 of the upper housing section 19.

It will be noted that the hub 32 of the holding spider initially has an inwardly directed flange 38 disposed across and incontact with the upwardly facing shoulder 39* of the valve guide 28. In view of such engagement, the valve guide 28 is prevented from moving upwardly by the holding spider 33, and this spider, in turn, is prevented from moving upwardly within the housing 13 by virtue of its engagement with the valve seat 35, that, in turn, engages the upper housing section 19. Simi larly, the valve seat 35 cannot move downwardly of the housing by engaging the holding spider 33, and the latter cannot move downwardly of the housing by virtue of its flange 38 engaging the guide 28, the downwardly facing shoulder 31 of the latter engaging the lower spider 24. With the parts arranged in this fashion, the valve guide 28, upper spider 33 and valve seat 35 are initially prevented from, moving in either longitudinal direction. The valve head or member 22, however, can move both in an upward and downward direction with respect to the valve guide 28 and the valve seat 35. This valve head is disposed between the upper and lower seats 20, 35 and is adapted to selectively engage these seats.

The valve head 22 has a central downwardly opening bore 39 to receive the upper piston portion 40 of the valve stem or guide 28. The bore constitutes a cylinder in which the pistonis slidable, the piston preferably carrying one or more piston rings or side seals 41 sealingly engaging the inner wall 42 of the bore or cylinder, to prevent the well bore fluid from entering the cylinder 39 above the piston 40. The cylinder above the piston is thereby maintained free of well bore fluid, and will initially contain air at substantially atmospheric pressure. The upper portion of the valve head 22 is an end. wall .43 constituting a closure for the cylinder or bore.

The valve head 22 is movable downwardly to engage its lower portion 44 with the annular valve seat 35. When so engaged, fluid is prevented from passing downwardly between the valve head 22 and seat 35. The valve head 22 can slide upwardly along the piston 40, to allow fluid to flow in an upward direction through the upper and lower spiders 24, 33, and through the valve seat '35, passing around the exterior of the valve head 22, and on up through the central passage 18 into the casing string B thereabove. Initially, the valve head 22 is prevented from moving upwardly into engagement with the upper valve seat 20 by a suitable stop element in the form of a pin 45 extending transversely through the lower portion of the valve head 22 and engageable with the lower end of the piston 40. I

When the valve head 22 is engaging the lower seat 35, the fluid in the well casing is acting in a downward direction over the cross-sectional area of the valve head at its line of contact with the valve seat. In view of the closed cylinder 39, which contains air at substantially atmospheric pressure, the fluid under pressure below the valve head 22 is acting in an upward direction across the annular cross-sectional area R of the valve head lying between the inner cylindrical wall 42 of the head and its line of contact with the lower valve seat 35 (Fig. 1). It is evident that the fluid within the well casing B is acting over a greater pressure effective area than the fluid externally of the well casing and below the. valve head 22. Accordingly, the valve head 22 will be shifted. downwardly into engagement with its.

seat when the pressure inside the well casing B is lower 4 than the pressure externally of the well casing, the difference in pressure, which corresponds to the difference in hydrostatic heads, being proportional to the ratio of the lower pressure effective annular area R and the upwardly facing pressure effective cross-sectional area S of the valve head.

With the relationship of the parts so far described, the valve head 22 is only effective to move out of engagement from its seat 35, and back into engagement with its seat, to either permit upward flow of fluid into the apparatus or to prevent downward flow of fluid in the apparatus. Such mode of action is desirable during lowering of the casing string through the fluid in the well bore. string at the desired depth in the well bore, fluid is to be pumped down through the casing B and out through the casing shoe A. When this occurs, the apparatus is operated to allow fluid to be pumped in a downward direction therethrough, and it is also placed in condition wherein the valve head 22 can move upwardly to a suflicient extent to engage the upper valve seat 20 and prevent upward passage of fluid back into the casing string B.

To accomplishthe purposes just noted, the inwardly directed flange 38 of the upper spider hub 32 is made disruptable. That is to say, it can be sheared from the main portion of the hub along the circumferential area 50, which will then allow the upper spider 33 and the lower seat 35 to drop downwardly within the intermediate housing section 23 to a substantial extent. The valve head 22 cannot move downwardly as far as the lower seat 35, in view of engagement of its end wall 43 with the upper end of the piston 40. Accordingly, there will be alongitudinal space between the valve head 22 and the lower seat 35 (Fig. 4) through which fluid can pass in a downward direction, the fluid continuing on through the lower seat 35 and through the spiders 33, 24 into the lower passage portion 18 through the cement plug- 14, and on out-of the well casing.

In view of the shearing of the inner flange 38 from the main body of the upper spider hub 32, the valve stem is no longer restrained against upward movement. Accordingly, should fluid tend to flow upwardly through the casing shoe A, it will carry the valve head 22 in an upward direction toward the upper seat 20, the stop pin 45 engaging the lower end of the piston 40 and lifting the valve stem or guide 28 with it to the extent required for the valve head 22 to engage the upper seat 20 (Fig.

In the operation of the apparatus, the parts are arranged in the manner disclosed in Fig. l, in which the valve guide 28 is prevented from moving in both longitudinal directions, the lower valve seat 35 being held in its upward position. As the well casing'B islowered through the fluid in the well bore, the hydrostatic head of fluid externally of the casing string can act on the downwardly facing surfaces of the valve head 22 to elevate it from its seat 35 to the extent limited by engagement of the stop pin 45 with the lower end of the piston 40 (Fig. 2). When the head is in this position, it is still prevented from engaging the upper valve seat 20. Accordingly, the fluid in the well bore can flow through the spiders 24, 33 and through the lower valve seat 35, passing around the head 22 and through the upper valve seat 20 into the central passage 18 and the casing string B. When thefluid in the well casing reaches a predetermined level, which will be less thanthe level of the fluid in the well bore externally of the well casing, such fluid will be effective over the greater upwardly projected area S of the valve head 22, to shift it downwardly into engagement with the valve seat 35, such asdisclosed in Fig. l, whereupon further upward passage of fluid is precluded. However, as the well casing B is lowered to greater depths, the valve. will again be opened (Fig. 2), to allow the well casing to fill with However, following the arrival of the casing acts in a downward direction over the cross-sectional area set the valve head 22, and also over the annular area of the valve seat 35, these parts exerting a combined downward force on the upper spider, 33. When the pressure is suflicient, this downward force will shear the inwardly directed flange 38 from the main body of the upper spider hub 32, thefluid under pressure within the well casingthen being effective to shift the head 22, seat 35and upper spider 33 downwardly within the housing 13. The upperspider 33 and valve seat 35 can move downwardly tb theiextent determined by engage-f ment of the upper spider with the lower spider 24.

Howeventhe valve head 22 cannot move this great a distance because its end wall 43 engages the upper end of piston 40, so that a substantial longitudinal space remains between the lower portion 44 of the valve head ahdthe lower seat 35, through which fluid can flow (Fig. 4). The fluidwithin the well casing can now pass downwardly through the casing shoe A, discharging therefrom and then passing in, an upward direction throughthe annulusbetween the exterior of the well casing B and thewallof the well bore. If desired, a charge of cement slurry 01' corresponding cementitious material may now be pumped down the casing string, passing through and from the casing shoe for deposition around and behind the string of well casing.

' In the event the pressure within the well leasing. is.

relieved and fluid tends to pass back into the well casing, the force of such fluid will carry the valve head.

22 and the valve stem 28 in an upward direction until the valve head engages the upper valve seat 20, thereby closing the casing shoe passage 18 against upward passage of fluid therethroughtFig. The upward movement of thehvalve head 22 to the extent just indicated is no longer prevented by the engagement of the stop pin 45 with the lower end of the piston 49, inasmuch as the shearing of the flange 38 on the upper spider hub 32 removed the restraint to upward movement on the valve guide or stem 28. s i s At any time, fluid can be pumped downwardly through the shoe A, the valve head 22 being merely shifted off its upper seat 20, but this head will again reengage this seat in the event upward passage of fluid tends to occur. I

With the arrangement disclosed, it is unnecessary to machine the parts to close tolerances, except possibly for the fit of the piston 40 within the cylinder bore 39 of the valve head .22. Leakage around the valve seat 35 i can be prevented by a suitable side seal 51, such as a rubber O ring, snugly engaging its periphery and dis: posed in a groove 52 provided between the upper and intermediate housing sectiohs 19, 2 3. The engagement between the lower valve seat 35 and the lower portion 44 of the valve head is substantially along a circumferential line of contact, which provides a very effective metallic seal between the parts. A similar line contact is provided between theupwardly tapering surface 21 of the valve head 22 and the upper valve seat 20. Not only can the apparatus be mademore economically, in view ofthe lack of any necessity for maintaining close tolerances, but the parts of the apparatus are easily movable.

About the only friction encountered is between the pistonseal rings 41 and the cylindrical wall 42 of the valve head 22, but the piston has a comparatively small diameter, so that the area of contact between the seal rings and the cylinder wall relatively small. The head 22 is accordingly, free to move a comparatively easy.

fashion in both an upward and downward direction relative to the valve guide or stem 28, and canmove very quickly into and out of engagement with the lower valve seat 35. i

It is to be noted that the valve head 22 functions to control the automatic filling of the well casing with fluid and also as a back pressure valve element. It is unnecessary to provide separate valvemembers to accomplish the; controllable filling and to subsequently prevent the upward passage of fluid through the well casing. For that reason, the over-all length of the casing shoeor corresponding apparatus can be made comparatively short. That is to say, the tubular member 10 is much shorter than was heretofore necessary, as well as theparts internally thereof. Here again, great economies in manufacture are possible.

After the well casing has been cemented in place, it is usual practice to drill out the internal mechanism of the casing shoe. In the present instance, such drilling is facilitatedby making substantially all of the parts of readily drillable materials, such as a magnesium alloy, aluminum alloy, cast iron, and the like. The parts are readily broken under the action of a drill bit and can be flushed from the well bore by the drilling fluid. The

drilling away of the internal mechanism will be facilitated if it is made of magnesium alloy or aluminum alloy.

Actually, all parts can be made of such alloys except for the lower valve seat 35 and the portion 44 of the valve head 22 engaging this seat. The lower valve seat can be made of a harder material, such as cast iron, and the portion 44 of the valve head engaging this seat can also be made as a separate cast iron ringsuitably secured to the remaining portion of the valve head 22. About the only other part disclosed which is not made of material that is as readily drillable as the magnesium or aluminum alloy is the transverse stop pin 45, which may be made of steel. However, this pin is relatively small and presents no difliculty to the rapid disintegration of the parts and materials internally of the tubular member. This rapid disintegration is also facilitated by the fact that, ashas been indicated above, the combining of the functions of controllably filling the casing string and of preventing return flow of fluid into the well casing shortens the over-all length of the mechahism within the tubular member 10, as well as of the tubular member itself. There is lessmaterial to be drilled out than in corresponding devices. i

The inventor claimsz 1. In apparatus of the character described: a tubular member adapted to be secured to a conduit section to be disposed in a well bore; a valve seat. in said tubular member; a guide member within and carried by said tubular member; and a valve member telescoped over said guide member in leakproof relation with respect thereto to provide a confined space into which well bore fluid cannot enter, said valve member being slidable downwardly along said guide member into engagement with said seat, said valve member having a total resultant upwardly facing cross-sectional area subject to the pressure of fluid above said valvemember which is greater than the total resultant downwardlyfacing crosssectional area of said valve member subject to the pressure of fluid below said valve member.

2. In apparatus of the character described: a tubular member adapted to be securedto a conduit section to be disposed in a well bore; a valve seat in said tubular member; a guide member within and carried by said tubular member; a valve member telescoped over and means releasably supporting said valve seat in a position to be engaged by'said valve member, release of said means enabling said seat to move downwardly in said rubular'member' away from such position of engagement by said valve member. 7 v

3. In apparatus of the character described: a tubular member adapted to be secured to a conduit section to be disposed in a well bore; a valve seat in said tubular member; a guide member within and carried by said tubular member; a valve member telescoped over and slidable downwardly along said guide member into engagement with said seat, said valve member having a total resultant upwardly facing cross-sectional area subject to the pressure offluid above said valve member which is greater than the total resultant downwardly facing cross-sectional area of said valve member subject to the pressure of fluid below said valve member; and frangible means releasably supporting said valve seat in a position to be engaged by said valve member, said frangible means being disruptable by the pressure of fluid above and acting downwardly on said valve member and seat to enable said seat to move downwardly in said tubular member away from such position of engagement by said valve member.

4. In apparatus of the character described: a tubular member adapted to be secured to a conduit section to be disposed in a well bore; a valve seat in said tubular member; a guide member within and carried by said tubular member; a valve member telescoped over and slidable downwardly along said guide member into engagement with said seat; and means releasably supporting said valve seat in a position to be engaged by said valve member, release of said means enabling said seat to move downwardly in said tubular member away from such position of engagement by said valve member.

5. In apparatus of the character described: a tubular member adapted to be secured to a conduit section to be disposed in a well bore; a. valve seat in said tubular member; aguide member within and carried by said tubular member; alvalve member telescoped over and slidable downwardly along said guide member into engagement with said seat;and frangible means releasably supporting said valve seat in a position to be engaged by said valve member, saidfrangible means being disruptable by the pressure of fluid above and acting downwardly on said valve member and seat to enable said seat to move downwardly in said tubular member away from such position member; a valve member telescoped over and slidable downwardly along said guide member into engagement with said seat, said valve member having a total resultant upwardly facing cross-sectional area subject to the pressure of fluid above said valve member which is greater than the total resultant downwardly facing cross-sectional area of said valve member subject to the pressure of fluid below said valve member; and frangible means releasably supporting said valve seat from said guide member in a position to be engaged by said valve member, said frangible means being disruptable by the pressure of fluid above and acting downwardly on said valve member and seat to enable said seat to move downwardly in said tubular member away from such position of engagement by said valve member.

7. In apparatus of the character described: a tubular member adapted to be secured to a conduit section to be disposed in a well bore; a valve seat in said tubular member; a guide member within and carried by said tubular member; a valve member telescoped over and slidable downwardly along said guide member into engagement with said seat, said valve member having a total resultant upwardly facing cross-sectional area subject to the pressure of fluid above said' valve member which is greater than the total resultant downwardly facing. cross-sectional area of said valve member subject to the pressure of fluid below said valve member; and frangible means including a flange resting upon said guide member to releasably support said valve seat from said guide member ina position to be engaged by said valve member, said flange being shearable from the remainder of said frangible means by the pressure of fluid above and acting downwardly on said valve member and seat to enable said seat to move downwardly in said tubular member away from such position of engagement by said valve member.

8. In apparatus of the character described: a tubular member adapted to be secured to a conduit section to be disposed in a well bore; a supporting member secured in said tubular member; a guide member supported by and extending upwardly from said supporting member; a valve seat in said tubular member above said supporting member; frangible means releasablysupporting said. valve seat from said. guide member and in an upward position; and a valve member telescoped over and slidable downwardly along said guide member into engagement with said seat.

9. In apparatus of the character described: a tubularv member adapted to be secured to a conduit section to be disposed in a well bore; a supporting member secured in said tubular member; a guide member supported by and extending upwardly from said supporting member; a valve seat in said tubular member above said supporting member; frangible means releasably supporting said valve seat from said guide member and in an upward position; and a valve member telescoped over and slidable downwardly along said guide member into engagement with said seat, said valve member having a total resultant upwardly facing cross-sectional area subject to the pressure of fluid above said valve member which is greater than the total resultant downwardly facing cross-sectional area of said valve member subject to the pressure of fluid below said valve member.

10. In apparatus of the character described: a tubular member adapted to be secured to a conduit section to be disposed in a well bore; a lower supporting member secured in said tubular member; a guide member supported by and extending upwardly from said lower supporting member; a valve seat in said tubular member above said lower supporting member; an upper member holding said valve seat in an upward position; frangible means supporting said upper member from said guide member; and a valve member telescoped over and slidable downwardly along said guide member into engagement with said seat.

11. In apparatus of the character described: a tubular member adapted to be secured to a conduit section to be disposed in a'well bore; an upper valve seat in said tubular member; a lower valve seat insaid tubular member; a guide member within and carried by said tubular memher; a valve member telescoped over and slidable along said guide member downwardly into engagement with said lower seat and upwardly into engagement with said upper seat; releasable means 'engageable with said valve member to prevent its engagement with said upper seat; and means for releasing said releasable means.

12. In apparatus of the character described: a tubular member adapted to be secured to a conduit section to be disposed in a well bore; an upper valve seat in said tubular member; a lower valve seat in said tubular member; a guide member within and carried by said tubular member; a valve member telescoped over and slidable along,

to be engaged by said valve member, release of said releasable supporting means enabling said lower valve seat to move downwardly in said tubular member away from such position of engagement by said valve member.

13. In apparatus of the character described: a tubular member adapted to be secured to a conduit section to be disposed in a well bore; an upper valve seat in said tubular member; a lower valve seat in said tubular member; a guide member within and carried by said tubular member; a valve member telescoped over and slidable along said guide member downwardly into engagement with said lower seat and upwardly into engagement with said upper seat; coengageable means on said valve member and guide to prevent upward movement of said valve member into engagement with said upper seat; and releasable means engaging said guide member to prevent upward movement of said guide member in said tubular member, release of said releasable means allowing said guide member to move upwardly in said tubular member to allow said valve member to engage said upper seat.

14. In apparatus of the character described: a tubular member adapted to be secured to a conduit section to be disposed in a well bore; an upper valve seat in said tubular member; a lower valve seat in said tubular member; a guide member within and carried by said tubular member; a valve member telescoped over and slidable along said guide member downwardly into engagement with said lower seat and upwardly into engagement with said upper seat; coengageable means on said valve memher and guide member to prevent upward movement of said valve member into engagement with said upper seat; and means releasably supporting said lower valve seat in a position to be engaged by said valve member, said releasable means engaging said guide member to prevent upward movement of said guide member within said tubular member, release of said means enabling said lower seat to move downwardly in said tubular member away from such position of engagement by said valve member and allowing said guide member to move upwardly to permit said valve member to engage said upper seat.

15. In apparatus of the character described: a tubular member adapted to be secured to a conduit section to be disposed in a well bore; a lower supporting member secured in said tubular member; a guide member sup ported by and extending upwardly from said lower supporting member; an upper valve seat in said tubular member; a lower valve seat in said tubular member; a valve member telescoped over and slidable along said guide member downwardly into engagement with said lower seat and upwardly into engagement with saidupper seat; an upper member holding said lower valve seat in an upward position to be engaged by said valve member, said upper member engaging and holding said guide member in a lower position within said tubular member; said upper member having frangible means thereon supporting said upper member from said guide member; coengageable means on said valve member and guide member to prevent upward movement of said valve member into engagement with said upper seat; said frangible means being disrupted by the pressure of fluid above and acting downwardly on said valve member and lower seat to enable said lower seat to move downwardly in said tubular member away from a position of engagement by said valve, member and also enabling said guide member to move upwardly to permit said valve member to move upwardly into engagement with said upper seat.

References Cited in the file of this patent UNITED STATES PATENTS 

